Ipronidazole, which chemically is 1-methyl-2-isopropyl-5-nitroimidazole, is a known compound. The preparation of this compound and its water-soluble salts are set out in U.S. Pat. No. 3,634,446 issued Jan. 11, 1972. Ipronidazole is highly useful in the field of veterinary medicine as it is active as an antiprotozoal and antihistomonal agent, particularly in the treatment of turkey blackhead disease or enterohepatitis. Ipronidazole is further useful in the prophylaxis and treatment of swine dysentery.
Due to the low water solubility of ipronidazole, water-soluble pharmaceutically acceptable acid addition salts thereof, preferably the hydrochloride, must be utilized when it is to be administered parenterally or in solution, e.g. in drinking water. A hinderance in the utilization of this highly active compound in solution, however, is that the shelf life of aqueous, physiologically compatible solutions of the aforementioned salts is limited by their low chemical stability. It has now been found in accordance with the present invention that aqueous solutions of free ipronidazole can be prepared which are physiologically compatible and which are not characterized by the instability demonstrated by aqueous solutions of the pharmaceutically acceptable acid addition salts thereof.